I think one of the biggest issues with the influence system and how it relates to item acquisitions is the break of immersion that comes when you fail an easy roll due to bad luck. An affluent Inquisitorial agent coming up short on the money for a box of autogun rounds is a little immersion shattering, to say the least. I have an idea to prevent those situations, in the form of these rules;
Direct Purchases
Some goods and services are so cheap and simple to obtain that there's really no need to roll influence for their acquisition.
Compare your Influence bonus to the table. If an acquisition has an availability modifier (after applying any appropriate modifiers, including your Commerce skill) the same or easier than your listed Acquisition Threshold, you may successfully complete the acquisition without rolling against Influence. Acquisitions of this type may be completed IFb times per session.
This is fairly rough, and may well be a horrible idea, but I figured I'd post it up as food for thought. Opinions?